IPX/SPX (short for Internetwork Packet Exchange/Sequenced Packet Exchange) is a set of defunct networking protocols developed by Novell for its NetWare networks. IPX/SPX was supported up to and including the era of Windows XP, with later operating systems moving to the modern TCP/IP protocol suite.
Today, IPX/SPX has been mostly relegated to IT history as an early alternative to TCP/IP. It is only present in select legacy systems that have not been able to transition to TCP/IP due to technological limitations.
How IPX/SPX works
IPX/SPX is composed of two protocols working in tandem: the IPX is the network layer protocol responsible for addressing and routing packets between computers on a Novell NetWare network, while SPX operates at the transport layer to deliver the packets between devices.
IPX addresses are hierarchical, consisting of a network address and a node address. The network address identifies the logical network, while the node address identifies the specific device on that network. Each device in a NetWare network has a unique IPX address. PX packets also include socket numbers to identify specific services on a device, allowing multiple applications on a single device to access network functions without conflict.